The Foundation of Freedom is the Courage of Ordinary People

History On Line

M3A1 .45 caliber
submachine gun and manual (Grease Gun)

The .45 caliber M3 is an automatic,
air-cooled blowback-operated weapon firing from an open
bolt, which is driven forward by the recoil springs,
stripping and chambering and firing a round in the same
motion. The M3A1 is an improved, simplified variant of
the M3. The low cyclical rate of fire and straight line
of recoil thrust provide excellent control and accuracy
for both weapons.

Adoption of the M3/M3A1 relegated
the Thompson submachine
gun to "Limited Standard" or
"Substitute Standard."

The widespread use of the Thompson
was due mainly to the fact that it was the only
allied submachine gun in mass production at the
beginning of WWII. It had several weaknesses; e.g.
weight and control. The Sten, for example, which was of
stamped and welded metal construction and finished
with a paint-like coating, scored higher than the
Thompson when such things as simplicity, accuracy,
weight and reliability were measured.

The .45 caliber M3 was an
automatic, air-cooled blowback-operated weapon that
fired from an open bolt. When the trigger is
pulled, the bolt is driven forward by the recoil
springs, stripping a round from the feed lips of
the magazine and guiding the round into the
chamber. The bolt then continues forward and the
firing pin strikes the cartridge primer, igniting
the round, resulting in a high-pressure impulse,
forcing the bolt back against the resistance of the
recoil springs and the inertial mass of the bolt.
By the time the bolt and empty casing have moved
far enough to the rear to open the chamber, the
bullet has left the barrel and pressure in the
barrel has dropped to a safe level. The low cyclic
rate was a function of the low pressure generated
by the .45 ACP round, a heavy bolt, and recoil
springs with a lighter-than-normal compression
rate.

The M3A1 is an improved, simplified
variant of the M3. Both are far easier to
manufacture than the Thompson, and have a number of
excellent design features in addition. The low
cyclical rate of fire makes the gun easier to
control than most submachine guns, not only the
Thompson. The weapon's straight line of recoil
thrust also adds substantially in controlling the
gun in automatic fire. The gun's loose
tolerances allow for reliable operation even if
very dirty and, with its bolt and guide rod design
make it more reliable than the Thompson under
adverse conditions.

The M3 and M3A1 submachine gun have
no mechanical means of locking the trigger. When
the magazine has been emptied, the bolt will close
on the empty chamber. Inserting a loaded magazine
loads the gun. If the cover is open and the bolt
cocked, pressure on the trigger will fire the gun.
If an unlocked gun is dropped, it may fire whether
the bolt is cocked or not.

The M3/M3A1 is only capable of
fully automatic operation; however, with its slow
rate of fire, an experienced shooter can squeeze
off single rounds.

"I carried a grease gun in Vietnam
while I served with the First Marine Division (66-68).
There are a several of neat things about the gun that
don't appear in the description and I'd like to
tell you about them. The gun had a built-in oiler in
the base of the grip. After turning the gun over, the
knob seen in the illustration is unscrewed revealing an
oil reservoir and an oil applicator. The wire stock was
a masterpiece of American ingenuity. It was a wrench
for removing the barrel, the barrel had two grooves
machined into it into which the wire stock was placed
and then turned to loosen the barrel. One of the stock
rods was threaded at the forward end to take a bore
brush and drilled out to take a cleaning patch, and
finally, there was a small "L" shaped piece
of steel welded to the butt of the stock, as seen in
the illustration, that functioned as a magazine loader.
Trying to thumb load 30 rounds into the mag was a
chore. This twenty-eight dollar, or so, piece of
stamped, welded and machined metal was a beauty, on the
several occasions when I needed it, it never failed me.
"

Among the different types of submachine
guns used by the Chinese Communist forces during the
first year of the Korea War was their .45 cal Type 36 copy of the M3A1

The M3A1 is still in use in our armed
forces today. Not a bad record for a gun that
hasn't been manufactured for over 40 years!

Causes of the Korean Tragedy ... Failure of Leadership, Intelligence and Preparation